Electric circuit breaker having highpressure,low-velocity gas blast



y 1, 1969 J. BARKER ETAL 3,453,407

ELECTRIC CIRCUIT BREAKER HAVING HIGH-PRESSURE, LOW-VELOCITY GAS BLAST Filed April 13, 1966 Sheet 3e 30 F\G.1

My 1 1 J. BARKER Em 3,453,401

ELECTRIC CIRCUIT BREAKEH HAVING HIGH-PRESSURE, LOW-VELOCITY GAS BLAST Filed April 13, 1966 Sheet .Z of 4 FIG.2

y 1969 J. BARKER ETAL 3,453, 07

ELECTRIC CIRCUIT BREAKER HAVING HIGH-PRESSURE, LOW-VELOCITY GAS BLAST Filed April 1:, 1966 Sheet 3 of 4 FIG.3

y 1, 1969 J. BARKER ETAL 3,453,407

ELECTRIC CIRCUIT BREAKER HAVING HIGH-PRESSURE, LOW-VELOCITY GAS BLAST 4 Filed April 13, 1966 Sheet of 4 190 H64 5 27A y A 19 26A 15A 23A x I 25A 1 as 181 l \5 29 HA i 3O u x u 35 United States Patent 3,453,407 ELECTRIC CIRCUIT BREAKER HAVING HIGH- PRESSURE, LOW-VELOCITY GAS BLAST John Barker, Stanislaw Mieczyslaw Gonek, and Kenneth George Love, Stafford, England, assignors to The English Electric Company Limited, London, England, a company of Great Britain Filed Apr. 13, 1966, Ser. No. 542,264 Claims priority, application Great Britain, Apr. 13, 1965, 15,819/65; Mar. 4, 1966, 9,712/66 Int. Cl. H01h 33/82, 33/14, 9/40 US. Cl. 200-148 6 Claims ABSTRACT OF THE DISCLOSURE A gas-blast electric circuit breaker having a gas receiver containing gas at a high pressure (e.g. 1,000 psi.) mounted on a support insulator to isolate it electrically from earth potential, and having a compressor which is operated in timed relation to the operation of the contacts to further compress the gas (e.g. by a further 300 p.s.i.) and to deliver a gas blast to the enclosure in which the contacts are located; the gas passing at low velocity between the contacts and through one contact, which is in the form of a hollow sleeve, thus removing gas ionized by the arc struck between the contacts as they separate, and the gas being returned to the gas receiver.

The receiver is preferably divided into two chambers by a perforated battle or, alternatively, it may be in the form of two separate vessels.

This invention relates to gas-blast electric circuit breakers.

According to the invention, a gas-blast electric circuit breaker includes a pair of relatively-movable contacts in an enclosure, gas receiver means containing gas at a high pressure, pump means to draw gas from the gas receiver means, and to deliver it to the enclosure to pass between the contacts when an arc is drawn between them on operation of the contacts, thereby to remove ionized gas from the region of the contacts, and means to lead ionized gas back to the gas receiver means.

One object of the invention is to provide a circuit breaker for use at high voltage, which has a higher current-interrupting capacity than known circuit breakers. The latter include air-blast circuit breakers, as disclosed in U.S. Patents Nos. 3,163,737 (Gonek et a1.) and 3,167,- 630 (Alderman et al.), in which the circuit breaker is pressurized by air at a pressure of, say, 300 lb./sq. in., a high-velocity blast through throat contacts being caused by the opening of an exhaust valve which vents the air to atmosphere. By contrast with such air-blast circuit breakers, the present invention stores gas, preferably air, at a considerably higher pressure, and therefore at a correspondingly higher density; no exhaust valve is used, the gas being circulated in a closed circuit, by means of a pump or compressor; and the blast over the contacts is at a much higher pressure, but flows at a lower velocity than in the prior art.

The prior art also includes gas-blast circuit breakers using sulfur hexafluoride (SP as the working medium; such gas is not capable of being used at the pressure employed in the present invention, as it would liquefy before reaching such pressure; moreover such circuit breakers, as disclosed for example in British Patent 736,090, employ a high-velocity gas blast, at low pressure, in contradistinction from the present invention.

Preferably in the constructions of the present invention the pump means is a reciprocating pump, for example, a piston and cylinder, and preferably it is arranged to ice operate in timed relation with movement of the movable contact or contacts. For example the pump may be connected through a mechanical linkage to the movable contact or contacts, or may be linked pneumatically thereto; in the latter case pneumatic piston and cylinder devices operating the contact and the pump may be controlled by a common valve.

Preferably the gas is air, though it may be any other suitable fluid which remains in gaseous form at the high pressures involved (of the order of 1,000 lb./sq. in.) and which has good arc-extinction characteristics.

The high pressure may be as low as 500 lb./sq. in., but is preferably at least 1,000 lb./sq. in. and in the preferred embodiment is 1,500 lb./sq. in. This pressure is preferably increased by at least lb./sq. in. by the pump means (the instantaneous pressure being measured immediately downstream of the pump means) and in the preferred embodiment it is increased by 300 lb./sq. in.

The gas receiver means may include two separate vessels, the pump means drawing gas from one and the ionized gas being led back to the other, the vessels being suitably interconnected. The enclosure containing the contacts may in this case conveniently be between the two vessels.

A number of embodiments of the invention will now be described with reference to the accompanying drawings, of which:

FIG. 1 is a diagrammatic section of a first embodiment of circuit breaker,

FIG. 2 is a view similar to FIG. 1 of a second embodiment of circuit breaker,

FIG. 3 is a detail of part of FIG. 2 on a larger scale, and

FIG. 4 is a third embodiment, which is a modification of that of FIG. 2.

Referring to FIG. 1, the circuit breaker has an interrupter unit 11 mounted on a generally spherical receiver 13 of conducting material, which is mounted on a suitable support insulator 14 to isolate it from earth potential.

The interrupter unit 11 has a top cap 15 spaced from a flanged base member 16 of the unit by an insulator 17. The base member 16 is bolted to the receiver 13. Although only a simple shedded porcelain insulator 17 is shown, for the sake of simplicity, the insulator will in practice also have an inner pressure-resistant tube, for example as described and claimed in British Patent No. 1,022,291.

The top cap 15 and base member 16 are provided with connections 15A. 16A to the line or to further circuit breakers in series in the line to be interrupted.

The fixed contact 21 of the interrupter unit comprises a sleeve 22 secured to the top cap 15 and extending inward and a cylindrical contact member 24 which slides within the sleeve 22 and is loaded by a spring 27 interposed between the contact member 24 and the top cap 15 to urge the contact member 24 to the position in which it extends beyond the end of the sleeve 22. A stop is provided to limit the travel of contact member 24. It will be understood that this assembly, although it has moving parts, is known in the art as the fixed contact.

The moving contact 28 comprises a sleeve 29 open at both ends and sliding in a fixed sleeve 30 secured to a member 31 forming part of the wall of the receiver 13. The sleeve 29 is supported by a spider on a rod 32, which is connected to an operating piston 33 working in a cylinder 34 which is fixed with respect to the receiver 13.

The receiver 13 is divided on its horizontal diameter by a perforated baffle or partition 35 which allows the pressure in the two halves of the receiver to equalize, but nevertheless prevents or restricts a general flow of gas from one half to the other.

From the hollow interior of the sleeve or throat contact 29, a passage 36 leads through sleeve and member 31 to a filter 37, gas from passage 36 passing through the filter element and exhausting into the top half of the receiver 13.

The space 38 within the insulator 17 and surrounding the contacts 21, 28 is connected by a passage 39 through member 31 to a compressor 40, comprising a piston 41 in a cylinder 42, mounted vertically (as shown) within receiver 13. A springloaded relief and non-return valve 43 is provided in the passage 39 at the outlet of cylinder 42, at its top end, and there is also provided a non-return valve 44 to allow gas to flow through pipe 45 into the cylinder 42 but to prevent flow in the reverse direction. The pipe 45 is connected between the cylinder 42 and the bottom half of the receiver 13 at a point far from the exhaust of the filter 37. A light return spring 46 loads the piston 41 downward (as seen in the drawing).

The stem 47 of piston 41 extends into a coaxial cylinder 48 and is secured to a piston 49 therein.

The cylinder space below piston 49 is connected by a pipe 80 to a trip valve 81, and the cylinder space above piston 49 is connected by a pipe 82 to a space at atmospheric pressure between the support insulator 14 and an inner cylindrical sleeve 83. The interior of sleeve 83 communicates between a source of high pressure at the base of the support insulator 14 and the interior of the receiver 13 Movement of piston 33 in cylinder 34 in one sense is controlled by the trip valve 81, and in the other sense by a close valve 84. A pipe 85 from the lower end of cylinder 34 leads to the trip valve 81, and a pipe 86 from the upper end of the cylinder 34 leads to the close valve 84 The trip valve 81 also has a connection 87 to the pressure space within the receiver 13, and a connection 88 to the space between support insulator 14 and sleeve 83. The close valve 84 also has a connection 89 to the pressure space, and a connection 90 to the space at atmospheric pressure.

In its normal position, to which its movable element is spring-loaded, the trip valve 81 connects the pipe 85 to connection 87, to subject the lower side of piston 33 to the high pressure within the receiver 13, and also connects pipe 80 to connection 88, to exhaust the cylinder space below piston 49 to atmospheric pressure. When the movable element of the trip valve 81 is moved to the right as shown in the drawing, the valve connects pipe 85 to connection 88, to exhaust the space below piston 33 to atmospheric pressure, and also connects pipe 80 to connection 87, to subject the space below piston 49 to the high pressure within receiver 13.

The close valve 84 connects pipe 86 to connection 89, in the normal position to which its movable element is spring-loaded, so as to subject the space above piston 33 to the high pressure in receiver 13. When the movable element of the close valve 84 is moved to the left as shown in the drawing, the valve connects pipe 86 to connection 90, so as to exhaust the space above piston 33 to atmospheric pressure.

The valves 81, 84 are actuated by an operating mechanism in the form of a rod 91, having ends which cooperate with the heads of the movable valve elements to operate them. One arm of a bell-crank lever 92 is pivotally connected to the centre of the rod 91, the other arm being connected to the end of an operating rod 93, which passes centrally through the sleeve 83.

The fulcrum of bell-crank lever 92 may be supported by a further mechanism, as described and claimed in British Patent No. 1,023,151, which is operated on completion of the movement of the movable contact member 28 to reset the rod 91 to its central position. This mechanism is preferably a mechanically linkage between the rod 32 and the fulcrum of bell-crank lever 92.

The pressure in the receiver 13 is preferably of the order of 1,500 lb./sq. in. and this is increased in the compressor 40 to a pressure of the order of 1,800 lb./sq. in., to which the contacts 21, 28 are subjected on operation of the circuit breaker, the greater part of the pressure drop in this circuit occurring in the filter 37. The density of the gas is thus approximately times atmospheric density in receiver 13, and times atmospheric density at delivery from the compressor.

The operating rod 93 is held, either directly or through a linked mechanism, by a detent (not shown) at the base of the support column 14, so arranged that, when the detent is released, the rod 93 moves rapidly upwards to trip the circuit-breaker. The bell-crank lever 92 is rocked anticlockwise, moving the rod 91 to the right and operating trip valve 81. The close valve 84 is unaffected by this operation. The trip valve 81 thus places the cylinder space below piston 49 in communication with the high pressure in receiver 13, and therefore piston 49 moves rapidly upwards. The trip valve 81 also places the space at the lower end of cylinder 34 in communication with atmosphere, and piston 33 therefore moves simultaneously downwards.

The movable contact 28 is moved from the closed to the open position, and compressor piston 41 is forced upwards, compressing the air in cylinder 42 to a pressure of the order of 1,800 lb./sq. in. and forcing it through valve 43 and along passage 39 to space 38 surrounding the contacts 21, 28 of the interrupter unit 11.

The air is at a density of some 120 times atmospheric density, and therefore although it flows at a low velocity in space 38, and between the contacts as they operate, and through passage 36, there is a large mass flow which removes ionized gas and the products of any are struck between the contacts. Moreover, the high pressure has been found to give good dielectric strength recovery characteristics.

As the sleeve 29 of the movable contact accelerates away from the closed position, the cylindrical contact member 24 remains in contact with it, urged by spring 27, until after the sleeve 29 has broken contact with the fixed sleeve contact 22. As the cylindrical contact member 24 comes to the end of its stroke, the sleeve 29 continues and the circuit is broken.

Movement of contact 28 to the open position may be arranged to reset operating rod 91 in its central position, as described and claimed in British Patent No. 1,023,151, thus allowing trip valve 81 to return to its normal position under the influence of its spring.

Movement of the operating rod 93 downwards, which may be achieved by any suitable mechanism, preferably housed at the base of the support insulator 14, closes the circuit breaker. This movement rocks bell-crank lever 92 clockwise, moving rod 91 to the left and operating close valve 84. The latter vents the cylinder space above piston 33 to atmospheric pressure, and therefore piston 33 moves upwards and moves contact 28 from the open to the closed position. This movement may also be arranged to reset the operating rod 91 to its central position, as described in the patent referred to.

Referring now to FIG. 2, the circuit-breaker of this embodiment has two interrupter units 11, 12, only one of which is shown in detail. It will be understood that the same reference numerals are used to indicate the same parts as in FIG. 1, and that the arrangement is virtually symmetrical, having a single control system, the connections to the interrupter unit 12 which is not shown in do tail being similar to the connections to the unit 11.

The interrupter units 11, 12 are mounted at an angle to one another (sixty degrees as shown) on a generally spherical receiver 13 of conducting material, which is mounted on a suitable support insulator 14 to isolate it from earth potential.

Each interrupter unit 11, 12 has a top cap 15 spaced from a flanged base member 16 of the unit by an insulator 17, which may be of porcelain. The base member 16 is bolted to the receiver 13, and the porcelain 17 may be held in compression between the top cap and base member 16 by means of a glass-fibre sleeve in tension, as described and claimed in British Patent No. 1,022,291. The sleeve is secured to end rings which abut or are secured to the top cap 15 and base member 16 respectively in a manner to allow adjustment of the tension.

The top caps 15 of the interrupter units 11, 12 are provided with connections to the line, or to further circuit breakers in series in the line to be interrupted.

The fixed contact 21 of each interrupter unit comprises a sleeve 22 secured to the top cap 15 and extending inward, and there is a second sleeve 23 coaxially within it. A cylindrical contact member 24 slides in the space between the sleeves, and has a stem 25 extending through a hole in the end of the inner sleeve 23 and connected to a piston 26 sliding within the inner sleeve. A spring 27 interposed between the piston 26 and the closed end of the outer sleeve 22 urges the contact member 24 to the position in which it extends out somewhat beyond the end of the outer sleeve 22. It will be understood that, although this assembly has moving parts, it is known in the art as the fixed contact. The moving contact 28 comprises a sleeve 29 open at both ends and sliding in a fixed sleeve 30 secured to a member 31 forming part of the Wall of the receiver 13. The sleeve 29 is supported by a spider on a rod 32, which is connected to the operating piston 33 (FIG. 3) working in a cylinder 34 solid with member 31.

The receiver 13 is divided on its horizontal diameter by a perforated bafile or partition 35 (FIG. 2) which allows the pressure in the two halves of the receiver to equalize, but nevertheless prevents or restricts a general flow of gas from one half to the other.

From the hollow interior of the sleeve or throat contact 29 a passage 36 leads through sleeve 30 and member 31 to a filter 37 mounted on the baffle 35, gas from passage 36 passing through the filter element and exhausting into the top half of the receiver.

The space 38 within the glass-fibre sleeve and surrounding the contacts 21, 28 is connected by a passage 39 (FIG. 3) through member 31 to a compressor 40, comprising a piston 41 in a cylinder 42, mounted on the vertical diameter of the receiver 13. A spring-loaded relief and nonreturn valve 43 is provided in the passage 39 at the outlet of cylinder 42, at its top end, and the piston 41 has a simple non-return valve 44 to allow gas to flow upward through the piston (as seen in the drawing) but to prevent fiow in the reverse direction. A pipe 45 is connected between the bottom of the cylinder 42 and the bottom half of the receiver 13 at a point far from the exhaust of the filter 37. A light return spring 46 loads the piston 41 downward.

The stem 47 of piston 41 extends into a coaxial cylinder 48 and is secured to a piston 49 therein. The cylinder space below piston 49 is open to the pressure in the receiver 13, but the space above the piston 49 is connected to a duct 50, controlled by a valve 51. In the position shown, communication between duct 50 and a pipe 52 leading to atmosphere (via the support column 14) is closed, and the duct 50 communicates through a port 53 with the interior of the receiver 13, so that receiver pressure is admitted to the cylinder space above piston 49. In its other position, the valve 51 closes off port 53 and allows duct 50 to communicate with pipe 52, so that the cylinder space above piston 49 is exhausted to atmosphere.

Valve 51 is controlled by piston 54 in cylinder 55, one side of the piston 54 being subject to receiver pressure and the other side being controlled by the trip valve 56; when the trip valve 56 is open the cylinder space is vented to atmosphere through pipe 52, and when it is closed valve 51 is loaded to move to the position shown.

Movement of piston 33 in cylinder 34 in one sense is controlled by valve 51, and in the other sense by a similar valve 57. A pipe 58 from the inner end of cylinder 34 leads to duct 50, so that when valve 51 is moved to the left, the inner end of the cylinder is vented to atmosphere, and when it is in the position shown, the inner end of the cylinder is open, through port 53, to receiver pressure. A pipe 59 from the outer end of the cylinder 34 leads to a duct 60; when valve 57 is moved to the right, duct 60 is placed in communication with pipe 52, and thus with atmosphere, by Way of an annular pipe 62 surrounding the valves 51, 57; and in the position shown, valve 57 places duct 60 in communication with the interior of receiver 13 through port 63, and shuts off the communication to atmosphere through pipes 62 and 52. Valve 57 is controlled by piston 64 in cylinder 65, one side of piston 64 being subject to receiver pressure and the other side being controlled by the close valve 66; when the close valve 66 is open the cylinder space is vented to atmosphere through pipe 52, and when it is closed valve 57 is loaded to move to the position shown.

The valves 55, 66 are actuated by an operating mechanism in the form of a tension rod 67, having forked ends which co-operate with the heads of the valve members to lift them; the valve members are normally loaded to the closed position by springs (omitted for clarity). One arm of a bell-crank lever 68 is pivotally connected to the centre of the tension rod 67, the other arm being connected to one abutment of a compression spring device 69, the other abutment of which is fixed. The operating rod 70, which passes centrally through a pressure gas supply pipe 71 within support insulator 14, is connected to the first-mentioned arm of the bell-crank lever 68 and is loaded in tension by spring device 69. The fulcrum of bell-crank lever 68 is pivoted to one arm of a second bellcrank lever 72, the fulcrum of which is pivotally mounted on the structure of the receiver 13, and the other arm of which is pivoted to a resetting rod 73. The other end of rod 73 is pivoted to a lever 74, the fulcrum of which is pivotally mounted on the receiver 13, and the other end of which engages with an extension of the piston rod 32. To accommodate the motion of the end of the lever 74 to the straight-line motion of rod 32, the lever 74 is made telescopic and spring-loaded into engagement with rod 32. A pin-and-slot connection could be used instead. The end of the rod 32 engages in a fixed guide 75.

The pressure in the receiver 13 is preferably of the order of 1,000 lb./sq. in., and this is increased in the compressor 40 to a pressure of the order of 1,300 lbs/sq. in., to which the contacts are subjected on operation of the compressor, the greater part of the pressure drop in this circuit occurring in the filter 37. The pipe 52 may be connected to atmosphere through an annular duct formed by a pipe inside the support insulator 14 and surrounding the pressure supply pipe 71; these pipes may be stressed in tension, as described and claimed in British Patent No. 1,022,291.

The operating rod 70 is held, either directly or through a linked mechanism, by a detent (not shown) at the base of the support column 14, so arranged that, when the detent is released, the rod 70 moves rapidly upwards to trip the circuit breaker, assisted by spring 69. The bell-crank lever 68 is rocked anti-clockwise, raising the tension rod 67 and opening trip valve 56. The close valve 66 is unaffected. Valve 56 vents the cylinder space on the left if piston 54 to atmosphere, and valve 51 therefore moves to the left, closing port 53 and allowing duct 50 to communicate with pipe 52. The pressure in cylinder 48 above piston 49, and also that at the inner end of cylinder 34 below piston 33, is vented to atmosphere, and therefore piston 49 moves up and piston 33 moves simultaneously inwards.

Moving contact 28 is moved from the closed to the open position, and compressor piston 41 is forced up, compressing the air in cylinder 42 to a pressure of the order of 1,300 lb./sq. in. and forcing it through valve 43 7 and along passage 39 to space 38 surrounding the contacts 21, 28 of each interrupter unit 11, 12.

The air is at a density of some 80-90 atmospheres, and therefore altthough it flows at a low velocity in space 38, between the contacts as they part, and through passage 36, there is a large mass flow which removes ionized gas and the products of any are struck between the contacts. Moreover the high pressure has been found to give good dielectric strength recovery characteristics. The ionized gas is discharged through filter 37 into the top half of the receiver 13. s

As the sleeve 29 of the movable contact accelerates away from the closed position, the cylindrical contact member 24 remains in contact with it, urged by spring 27, until after the sleeve 29 has broken contact with the fixed sleeve contact 22. As the piston 26 comes to the end of its stroke, the arcing contact member 24 is halted, the sleeve 29 continues, and the circuit is broken.

Movement of contact 28 to the open position rocks lever 74 about its fulcrum and, through rod 73, rocks bell-crank lever 72 anti-clockwise, thus rocking lever 68 clockwise, resetting the operating mechanism 67 in its central position and allowing valve 56 to close under the influence of its spring.

Movement of the Operating rod 70 downwards, which may be achieved by any suitable mechanism preferably housed at the base of the support insulator 14, closes the circuit breaker. This movement rocks lever 68 clockwise, lowering tension rod 67 and opening close valve 66. Valve 66 vents the cylinder space on the right of the piston 64 to atmosphere, and valve 57 therefore moves to the right, closing port 63 and allowing duct 60 to communicate, through pipe 62, with pipe 52. The pressure in the outer end of cylinder 34, above piston 33, is vented to atmosphere, and therefore piston 33 moves outwards and moves contact 28 from the open position to the closed position.

It will be understood that certain parts in the diagrammatic view of FIGS. 2 and 3 are shown in the plane of the paper for convenience and that, in fact, where two interrupter units 11, 12, are provided, these parts, e.g. pipes 45, 52, rod 67 and lever 68, may be in a plane at right angles to that in which they are shown, the linkage 72, 73, 74 being modified accordingly.

Th passage 36 from interrupter unit 12 may be connected to the corresponding passage from interrupter unit 11, to exhaust through the same filter 37.

Referring now to FIG. 4, there is shown a modification of the embodiment of FIGS. 2 and 3. Apart from the differences shown, this arrangement is identical to that of FIGS. 2 and 3. In FIG. 4 the same parts are given the same reference numerals, and similar (but not identical) parts have the postscript A.

The interrupter units 11A, 12A, and the spherical receiver 13A are mounted in the same manner as shown in FIG. 2, the receiver being mounted on a support insulator. In this case, however, a further receiver 180 of conructing material is associated with each interrupter unit. The further receiver 180 is secured to the top cap 15A, which is supported from the spherical receiver 13A by a porcelain insulator 17 in compression and a glass fibre sleeve 18 in tension; the two latter may be exactly as in the construction of FIG. 2. The line connection may be made to the further receiver 180 instead of to the top cap 15A.

A flange 181 on the further receiver 180 has the end rings 182, 183 on one end of, respectively, a porcelain insulator 184 and a glass-fibre reinforced resin sleeve 185 bolted to it, the end rings 182, 183 on the other ends of the insulator 184 and sleeve 185 respectively being bolted to a corresponding flange 186 on a metal pipe 187 welded to the spherical receiver 13A below the partition 35, the receiver being apertured so that the pipe 187 communicates with its interior. Suitable means are provided for adjusting the tension in the sleeve 185 and the compression in the insulator 184, which may be as described in British Patent No. 1,022,291.

The movable contact 28 is exactly as described with reference to FIG. 2, but the fixed contact 21A comprises a fixed sleeve member 22A, which is hollow to afford a passage 188, and which is secured by a flange to the further receiver 180. A hollow cylindrical contact member 24A slides in the sleeve member 22A and forms the arcing contact, the tip of the sleeve member 22A forming the main contact and operating as described with referetnce to FIGS. 1 and 2; the contact member 24A is supported by a spider on a stem 25A, which passes centrally down part of passage 188 and through a hole in the wall of the passage where the latter bends away. On the side of the wall outside passage 188 the stem 25A is connected to a piston 26A which, in its lowermost position as seen in the drawing, co-operates with a cylinder 23A to buffer downward movement of the contact member 24A. A spring 27A interposed between the piston 26A and an end closure part 189 secured to sleeve 22A urges the contact member 24A to the position in which it extends out somewhat beyond the end of the outer sleeve 22A.

The outlet of the passage 188 into the interior of the further receiver is provided with a filter 190.

Operation of the construction of FIG. 4 is exactly as described in relation to FIGS. 2 and 3, except that as the moving contact 28 moves from the closed to the open position, and the compressor piston 41 forces air to space 38 surrounding the contacts, the air flows not only through hollow sleeve 29 of the moving contact and passage 36, but also through hollow contact member 24A, passage 188 and filter 190 into the further receiver 180.

As the latter is in permanent communication through sleeve and pipe 187 with the spherical receiver 13A, air flows from receiver 180 to the spherical receiver 13A to equalize the pressures, though this takes place over a longer period of time than that during which a gas blast from compressor 40 is supplied to the contact region.

It will be noted that the point of connection of pipe 187 to the spherical receiver 13A is remote from the inlet to pipe 45, through which air is drawn into the compressor 40.

It will be understood that the compressor piston 41 is preferably caused, by the arrangement of the lengths and diameters of pipes 80, 85, to begin to move fractionally before the movable contact 28, so that air in cylinder 42 is compressed before the movable contact 28 separates from Contact member 24. In this way the contact member 24 need only have a short travel. However, piston 33 and piston 49 may, if desired, be arranged to begin to move simultaneously, in which case a longer travel of contact member 24 will be required in order to enable piston 41 to compress air in cylinder 42 to a pressure substantially above that in the receiver 13.

Preferably the cross-sectional area of the gas passage through the hollow contact (or contacts) is so dimensioned, and the pressure difference from upstream to downstream of the hollow contact (or contacts), as determined by the dimensions of the pump means, of the enclosure to which the gas is delivered, and of the path followed by the ionized gas back to the gas receiver means, is so arranged that the velocity of the gas flowing through the hollow contact (or contacts) is in the range 300 to 700 ft./sec., and is preferably of the order of 500 ft./sec. This subsonic velocity is low compared with the sonic velocity hitherto employed in the hollow contacts of gas-blast circuit-breakers; and the correspondingly low dynamic head results in a correspondingly higher static pressure within the hollow contact (or contacts) for a given total pressure. This enhances the effect of the high pressure produced by the pump means in giving a high dielectric strength between the contacts.

Moreover, despite the low velocity, there is a large mass flow of gas to remove the ionized arcing products.

We claim:

1. A gas-blast electric circuit breaker wherein the gas is preferably air comprising a tubular insulator, first and second members spaced apart by said tubular insulator, said tubular insulator and said first and second members together defining an enclosure;

a pair of relatively-movable contacts mounted within said enclosure, one at least of said contacts being in the form of a hollow sleeve contact;

gas receiver means containing gas at a pressure of at least 500 lb./sq. in. and correspondingly high density, and having said second member secured thereto;

support insulator means on which said gas receiver means is supported, said support insulator means isolating said gas receiver means from ground potential;

compressor means coupled to said movable contact and operable only upon movement of the movable contact, said compressor means mounted in communication with said gas receiver means and having an inlet through which gas is drawn from within said gas receiver means;

delivery passage means connected between said compressor means and said enclosure;

compressor-operating means connected to said compressor means to operate it;

contact-operating means connected to at least one of said contacts to cause relative movement of said contacts;

control means connected to said compressor-operating means and to said contact-operating means to cause operation of said compressor-operating means and said contact-operating means in timed relation;

and return passage means communicating in a closed circuit between the interior of said hollow sleeve contact and said gas receiver means;

whereby, in operation, said gas at a pressure of at least 500 lb./sq. in. is drawn from within said gas receiver means, is further compressed in said compressor means to a pressure which is at least 100 lb./ sq. in. higher than the pressure contained in said gas receiver means, and is delivered through said delivery passage means to said enclosure, so that, on separation of said relatively-movable contacts during current flow, said further compressed gas passes through said hollow sleeve contact, removing gas ionized by the arc struck between the contacts as they separate, and carrying said ionized gas through said return passage means to said gas receiver means.

2. A gas-blast electric circuit breaker comprising a tubular insulator, first and second members spaced apart by said tubular insulator, said tubular insulator and said first and second members together defining an enclosure;

a pair of relatively-movable contacts mounted within said enclosure, one at least of said contacts being in the form of a hollow sleeve contact;

gas receiver means containing gas at a pressure of at least 500 lb./sq. in. and correspondingly high density, and having said second member secured thereto; support insulator means on which said gas receiver means is supported, said support insulator means isolating said gas receiver means from ground potential;

compressor means mounted in communication with said gas receiver means and having'aninlet through which gas is drawn from within said gas receiver means; A

delivery passage means connected between said compressor means and said enclosure;

compressor-operating means connected to said compressor means to operate it;

contact-operating means connected to at least one of said contacts to cause relative movement of said contacts;

control means connected to said compressor-operating means and to said contact-operating means to cause operation of said compressor-operating means and said contact-operating means in timed relation;

return passage means communicating in a closed circuit between the interior of said hollow sleeve contact and said gas receiver means;

a perforated bathe in said gas receiver means and dividing said gas receiver means into two chambers, said perforated baffie allowing the pressure in said two chambers to equalize but restricting a general flow of gas from one chamber to the other;

wherein said inlet of said compressor means comprises pipe means opening into one said chamber and wherein said return passage means communicates with the other said chamber; whereby, in operation, said gas at a pressure of at least 500 lb./sq. in. is drawn from within said gas receiver means, is further compressed in said compressor means. and is delivered through said delivery passage to said enclosure, so that, on separation of said relatively-movable contacts during current fiow, said further compressed gas passes through said hollow sleeve contact, removing gas ionized by the arc struck between the contacts as they separate, and carrying said ionized gas through said return passage means to said gas receiver means.

3. A gas-blast electric circuit breaker as claimed in claim 2, comprising also filter means connected to said return passage means.

4. A gas-blast electric circuit breaker as claimed in claim 3, said compressor means comprising a cylinder, and a piston in said cylinder, and said inlet comprising a non-return valve through which gas is drawn into said cylinder; said delivery passage means comprising a nonreturn valve through which gas is delivered by said compressor means.

5. A gas-blast electric circuit breaker as claimed in claim 1, wherein said hollow sleeve contact is so designed that the velocity of gas fiow therethrough is substantially below sonic velocity.

6. A gas-blast electric circuit breaker wherein the gas is preferably air including means defining an enclosure,

a pair of relatively-movable contacts mounted within said enclosure, one at least of said contacts being in the form of a hollow sleeve contact,

gas receiver means containing gas at a pressure of at least 500 lb./sq. in.,

support insulator means to support said gas receiver means and isolate it from ground potential,

compressor means coupled to said movable contact and operable only upon movement of the movable contact, said compressor means connected to said gas receiver means to draw gas therefrom,

delivery passage means connected between said compressor means and said enclosure,

means to operate said compressor means to compress gas drawn from within said gas receiver means to a pressure which is at least lb./sq. in. higher than the pressure contained within said gas receiver means,

means to cause relative movement of said contacts in timed relation to operation of said compressor means,

and return passage means leading from the interior of said hollow sleeve contact in a closed circuit to said gas receiver means,

whereby, in operation, said gas at-a pressure of at least 500 lb./sq. in. is drawn from said gas receiver means, is further compressed in said compressor means,

1 1 1 Z and is delivered through said delivery passage means References Cited to said enclosure, so that, on separation of said con- UNITED STATES PATENTS tacts under load, said further compressed gas passes 3,275,778 9/1966 M Orioka.

through said hollow sleeve contact, removing gas ionized by the arc struck between the contacts, and 5 ROBERT MACON Primary Examinercarrying it through said return passage means to said U s CL gas receiver means. 200145 

